A number of cross-linking silicone emulsion compositions which cure into rubber coatings are known in the art, as disclosed in JP-A 5-98579 corresponding to USP 5,254,621, JP-A 8-85760, JP-A 9-208826 corresponding to U.S. Pat. No. 5,827,921, JP-A 2000-34410 corresponding to U.S. Pat. No. 6,140,414, and JP-A 2001-55510. Effective coating treatment is possible when these compositions are applied to fabrics, building members, and other substrates having an irregular surface. Problems arise, however, when they are applied to films, paper sheets, and other substrates having a relatively smooth surface to form a thin coating thereon. The coating weight will vary during the coating step, failing to form a coating having a uniform thickness.
Water- and oil-repellent paper sheets having a function of restraining oil penetration are commonly utilized as food packages and wrappers for packaging or wrapping oily food items such as fried items and oil and fat-containing foods. These water- and oil-repellent paper sheets are not only desired to be fully water- and oil-repellent, but must also be safe. A number of proposals are known in the art. Recently, those water- and oil-repellent paper sheets having organic fluororesins incorporated therein drew a concern about safety. As a substitute, those paper sheets having a water- and oil-repellent layer formed on a paper substrate were proposed as disclosed in JP-A 8-209590 and JP-A 9-87994.
As compared with the prior art water- and oil-repellent paper sheets having organic fluororesins incorporated therein, those paper sheets having a water- and oil-repellent layer formed on a paper substrate for insuring safety are difficult to provide a sufficient level of water and oil repellency. It is pointed out that particularly when the paper sheets are folded for use as boxes or base sheets, the folded portions suffer from noticeable losses of water and oil repellency.